He added: "The FTC is firmly and fully committed to using all of its tools to protect the privacy of consumers.

"Foremost among these tools is enforcement action against companies that fail to honor their privacy promises, including to comply with [transatlantic data sharing deal] Privacy Shield, or that engage in unfair acts that cause substantial injury to consumers in violation of the FTC Act."

Pahl also noted even companies that have "settled previous FTC actions must also comply with FTC order provisions imposing privacy and data security requirements" – a pointed reference to the consent decree Facebook agreed to in 2011, after admitting it "made mistakes" with user data at the time.

Confirmation of the FTC's probe knocked a chunk off Facebook's shares, with the firm trading at about 5.5 per cent down on the start of the day, reaching a low of $151.59 before recovering slightly.

Fleeing Facebook app users realise what they agreed to in apps years ago – total slurpage

This is compared with a share price of $156.39 at previous close, and highs of $183 before the scandal erupted.

News of the FTC comes after a weekend where the Zuckerborg took out full-page ads in UK and US newspapers to try to do some damage control, as the #deletefacebook movement continues to gain traction.

But things didn't quite go according to plan: some users deleting their accounts decided to fnd out what data Facebook actually stored on them, and to their horror realised Facebook Messenger on Android uploaded far more than expected, as well as metadata for phone calls and text messages that weren't made through Facebook's apps.

In response, Facebook was forced to issue another statement: "You may have seen some recent reports that Facebook has been logging people's call and SMS (text) history without their permission. This is not the case."

Why not? you may ask. Well, because technically Facebook did get permission from you – in those terms and conditions that everyone famously reads – and you could have opted out. And it's not like it collected the content of the calls and texts – just exactly when you made them, to anyone.

Continuing to miss the bigger picture, Facebook added: "Your information is securely stored and we do not sell this information to third parties. You are always in control of the information you share with Facebook." ®